Research Projects

The oblique subduction of the Indo-Australian Plate beneath the Southeast Asian Plate has given rise to a classic trench-forearc-volcanic arc-backarc system along Andaman-Nicobar-Sumatra (ANS) region. A series of submarine volcanoes of the volcanic arc system in the ANS region has been observed (Kamesh Raju et al., 2012; Aswini et al., 2024). Among these, the Cratered seamount (CSM) situated off Nicobar Islands, is a particularly intriguing feature believed to have been volcanically active in the recent past. Recent hydroacoustic observations reported hydrothermal plumes enriched with dissolved gases primarily CO₂ in the overlying water column & proposed that these gases are sourced from a subsurface magma chamber via dike intrusions (Sriram et al., 2023). Geochemical studies by Peketi et al. (2023) documented presence of living chemosymbiotic organisms, indicating a present supply of H2S and neoformed minerals such as amorphous silica, barite, and orpiment. The Off-Nicobar region has also experienced several earthquake swarms in 2005, 2014, 2015, and 2019 have been linked to active volcano-tectonic interactions (Špičák and Vaněk 2013; Aswini et al. 2021). Globally submarine volcanic regions host continuously replenished reservoirs of high-enthalpy hydrothermal fluids, offering substantial opportunities for hydrothermal energy. Notable examples include the Sumatra Arc, Mariana Arc, Okinawa Trough, Lesser Antilles, Marsili seamount hosting significant hydrothermal systems enriched with critical and rare earth elements (Chadwick et al., 2014; Carey et al., 2013; Italiano et al., 2014; Paltrinieri et al., 2022). The Andaman volcanic arc exhibits geochemical and tectonic similarities to these systems and could possess similar potential for hydrothermal energy and mineral exploration. For estimating and exploring the hydrothermal energy and mineral resource potential of such hydrothermally active seamounts, it is crucial to understand the subsurface structure and magma dynamics. Whereas, the CSM region is very less studied tectonically. Seismic data from 2014 OBS experiment (Dewangan et al., 2017) revealed a major earthquake (Mw 6.5, 21st March 2014) accompanied by swarms, along with signatures of very long-period events and hydroacoustic phases near the volcanic arc, Off-Nicobar suggesting unrest in the magma chamber. Analyses of earthquake swarms in the area indicated that the upward migration of magma likely induced strike-slip movement along sliver faults (Aswini et al., 2020, 2021). Despite such insights, in absence of the well resolved lithospheric structure of this region, key questions about the nature of the underlying lithosphere, the connectivity between seismic and magmatic activity, and the origin of hydrothermal plumes remain unresolved. To address this gap, the CSIR-National Institute of Oceanography undertook an integrated geophysical survey onboard RV Sindhu Sadhana in November 2021 and collected Multi-beam bathymetry, Gravity and Magnetic data along two profiles across CSM. In addition to acquired shipborne gravity data, we also use satellite gravity data for 3D density modelling. Subsequently deployed 13 temporary ocean bottom seismometers (OBSs) from 10th October 2023 to 20th January 2024. The current project intends to utilize integrated datasets passive OBS readings, gravity and magnetic anomalies to determine high resolution 3D geophysical models depicting the seismic velocity, density structure and 2D magnetic susceptibility of the lithosphere beneath the CSM. In this project, we shall use local earthquake, seismic ambient noise & surface wave tomography techniques, and joint inversion of gravity and magnetic datasets. This project aims to develop a comprehensive model of the lithosphere by integrating the interconnected geophysical attributes of the CSM region, this effort seeks to enhance our understanding of magma dynamics and its implications for hydrothermal discharge and seismo-tectonic activity.